192 clutches and power-stop control – Transmission and brake – Motor vehicle
Reexamination Certificate
1999-11-15
2001-06-05
Marmor, Charles A (Department: 3681)
192 clutches and power-stop control
Transmission and brake
Motor vehicle
Reexamination Certificate
active
06241068
ABSTRACT:
TECHNICAL FIELD
The subject invention relates generally to a shift lever assembly for a vehicle transmission. Specifically, the shift lever assembly includes an interlock mechanism that allows the shift lever to move out of a park position under pre-load conditions.
BACKGROUND OF THE INVENTION
The invention relates to a shift lever assembly used to shift a vehicle transmission between a plurality of shift positions. The invention is particularly directed to providing a shift lever assembly with an interlock that operates under pre-load conditions.
Brake transmission safety interlock (BTSI) systems are used to ensure that a vehicle braking system is activated before the transmission can be shifted out of a park position. In the prior art, BTSI systems typically include a shift lever device with a solenoid, a shift cable extending from the shift lever to the vehicle transmission, and an electromechanical device in electrical communication with the vehicle braking system and in mechanical communication with the shift cable. When the vehicle is in park and the vehicle braking system is at rest, the shift lever cannot be shifted out of park, and thus the shift cable cannot shift the transmission out of park. When the vehicle is in park and the vehicle braking system is activated, the shift lever can be moved out of park, causing the shift cable to shift the transmission.
One problem with such prior art BTSI systems is pre-load release. A pre-load release condition exists when an operator tries to shift out of park without first applying the brakes. The locking mechanism in the BTSI system is thus placed under load. As long as the operator maintains the shift load, the locking mechanism will fail to release and allow shifting even if the brakes are subsequently applied. In order to release the locking mechanism, the operator must remove the initial shift load, apply the brakes, and then shift out of park.
An example of a BTSI system with pre-load release is shown in U.S. Pat. No. 5,176,231. This system utilizes a solenoid with a plunger that is used to engage a notch having an S-shaped sigmoidal wall in a shift cable assembly. When the plunger is vertically extended into the notch, the cable does not move, and the transmission cannot be shifted. When the braking system is activated and the plunger is removed from the notch, the cable can move and the transmission can be shifted. Interaction of the plunger and the S-shaped sigmoidal wall of the notch allow shifting out of park under pre-load conditions.
BTSI systems such as these are difficult to package and install because the interlock mechanism is interacting directly with the shift cable. Shift cables are difficult to route through vehicles and the addition of an interlock mechanism on the cable further increases installation difficulties. Also, failures in interlock mechanism such as these can be difficult to service depending on where the interlock is mounted to the shift cable. The present invention provides a shift lever assembly for a BTSI system with an interlock that interacts directly with the selector lever and which can shift out of park even under pre-load conditions. The shift lever assembly is also easy to install and maintain.
SUMMARY OF THE INVENTION AND ADVANTAGES
A shift lever assembly for a vehicle transmission includes a housing and a detent supported within the housing, and a selector lever. The detent is selectively movable between a plurality of shift positions. The selector lever defines a longitudinal lever axis and is pivotally mounted with respect to the housing to move the detent between the shift positions. A stop engages a portion of the lever to prevent the lever from moving longitudinally along the axis. The assembly is characterized by including an actuator that moves the lever tangentially to the stop. This allows the lever to move along the longitudinal lever axis when a pre-determined condition is met, resulting in the detent moving from a first shift position to a second shift position.
Preferably, the selector lever is prevented from moving out of a park shift position until the vehicle brakes are applied. In a preferred embodiment, the detent is comprised of a fixed member with a plurality of detent gates corresponding to the shift positions and a pawl mounted to the selector lever for movement into and out of the detent gates. Sometimes, a shift force is applied to the selector lever before the brakes are applied causing a pre-load condition between the pawl and the detent gate. In the preferred embodiment, the selector lever includes a roller mounted to one end that engages the stop. The actuator can move the lever tangentially to the stop when the brakes are applied even when the pawl is under a pre-load condition.
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Commercial activity statement and supporting documents.
Howard & Howard
Marmor Charles A
Rodríguez Saúd
Teleflex Incorporated
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